1. Field of the Invention
The present invention relates to a plasma generator, and particularly to a plasma generator suitable for use, for example, in decomposing or removing substances harmful to the human body, which are contained in the air, by generating plasma by discharge between a pair of electrodes to form activated species.
2. Description of the Background Art
At present, plasma is considered to be useful as a medium capable of effectively removing or decomposing harmful substances contained in the air, for example, bacteria, viruses, pollen and/or the like, to make them harmless, since ions or activated species such as radicals formed by an electronic collision in the plasma facilitate chemical reactions with other atoms or molecules, and is thus used in, for example, deodorizing apparatus, bactericidal apparatus, air cleaning apparatus and the like (see, for example, Japanese Patent Application Laid-Open Nos. 2002-1055, 2003-135571 and 2002-78788).
Some plasma generators making up such deodorizing apparatus and air cleaning apparatus are constructed by providing an electrode structure that a pair of electrodes 31 and 32 are arranged in opposed relation to each other in a state that central positions C1 and C2 in arrangement of these electrodes are aligned with each other through a dielectric 30 composed of, for example, ceramic or quartz glass as illustrated in FIG. 6, and plasma is generated along the surface(s) of the dielectric 30 by discharge caused by applying voltage between the electrodes 31 and 32.
In the plasma generator utilizing the discharge (gaseous discharge) making use of the dielectric, however, ozone is unavoidably generated with the discharge between the electrodes. Since ozone is harmful to the human body, it is necessary to prevent or control the generation of ozone in the case where such a plasma generator is applied to, for example, a deodorizing apparatus, bactericidal apparatus or air cleaning apparatus. The environmental criteria as to ozone prescribed by, for example, Japan Air Cleaning Association is at most 0.05 ppm.